Some interesting views on MySpace and un-design live here: "Granted, the visual design of MySpace is simplistic, brutely exposing its content. But is that a knock against it, or a compliment to it?"

But two things I note:

• The *really* successful social sites (which I'll define, for the sake of argument, as the ones I use) are the ones where social activity is a by-product of some other benefit: image sharing for Flickr, diaries for LiveJournal, etc. Compare the links of LinkedIn and Orkut which are much more explicitly social... and much less useful from what I see.

• Isn't the big win about MySpace the music-related side of it - the instant association of music with people, which I'd guess resonates well with a teenage audience and explains why it's been a hit at the grassroots end of the music industry?
  

i.e. maybe it's not about "designing a social site" at all, in a visual sense, and much of the MySpace design is experienced not in the look and feel of its pages but in the constant association of audio with its users.